164 Frequency Synthesizer Fault Finding TP9100 Service Manual
© Tait Electronics Limited May 2005
Task 3 —
14V Power Supply
First check the output VCL SUPPLY from the SMPS, which is itself provided
with a 7
V5 LINK DC supply.
1. Remove the main board from the chassis.
2. Place the radio in CCTM.
3. Measure the SMPS output
VCL SUPPLY at the junction between C531
and R530 (see Figure 9.2).
Note The fault could also be caused by the load shorted to ground.
With power off, measure the resistance to ground at the junction
of C531 and R530. It should be approx. 117kΩ.
4. If the SMPS output is correct, go to Ta s k 4
. If it is not, go to Step 5.
5. Check the 7
V5 LINK supply at R533 and 3VO AN at E2 of Q500
(see Figure 9.2).
6. If the voltages are correct, go to Step 7. If it is not, the 7.5V supply
is faulty. Go to “Power Supply Fault Finding” on page 149.
7. Check the SMPS circuit based on Q500 and L502 (see Figure 9.2).
8. If a fault is found, repair the circuit, confirm the removal of the fault,
and go to “Final Tasks” on page 134. If the repair failed or no fault
could be found, replace the main board, and go to “Final Tasks” on
page 134.
C531: 14.9V ± 0.2 DC at room temperature
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